We have been evaluating the data we have collected for our action spectrum of DNA synthesis inhibition to determine the excitation order, n, using the general dose-response equation, , where S is the normalized survival and the dose, D, is defined as Int. (The irradiance, I, is in photons/s((m2, and n is the number of photons required for a single excitation event, or the excitation order.) Preliminary analysis suggests that the observed damage is arising from different absorbing species at different wavelengths -- at 700 nm damage appears to be from one-photon events and at 740 nm it appears to be from two-photon events. Further studies are underway to confirm this observation.